Extracellular vesicles in parasitic diseases

Abstract

Parasitic diseases affect billions of people and are considered a major public health issue. Close to 400 species are estimated to parasitize humans, of which around 90 are responsible for great clinical burden and mortality rates. Unfortunately, they are largely neglected as they are mainly endemic to poor regions. Of relevance to this review, there is accumulating evidence of the release of extracellular vesicles (EVs) in parasitic diseases, acting both in parasite-parasite inter-communication as well as in parasite-host interactions. EVs participate in the dissemination of the pathogen and play a role in the regulation of the host immune systems. Production of EVs from parasites or parasitized cells has been described for a number of parasitic infections. In this review, we provide the most relevant findings of the involvement of EVs in intercellular communication, modulation of immune responses, involvement in pathology, and their potential as new diagnostic tools and therapeutic agents in some of the major human parasitic pathogens.

Keywords: exosomes; extracellular vesicles; helminths; microvesicles; parasites; protozoa.

Fig. 1

Endemic geographical distribution of some human parasitic diseases. The map shows 5 different areas of the world according to WHO: Americas, Africa, Europe, Eastern Mediterranean and South-East Asia Western Pacific. The percentages represent the distribution of autochthonous endemic cases (133).

Fig. 2

Extracellular vesicles (EVs) and parasitic diseases. Two major groups of parasitic diseases, protozoa and helminths, as reviewed here actively secrete EVs of endocytic origin (exosomes, 40–100 nm) or membrane budding (microvesicles, 100 nm⁻¹ µM). As illustrated here with selected examples, they can act in different biological/pathological processes or potentially used to discover new biomarkers for diagnostics or as cell-free vaccines. (A) Intercellular communication mediated by exosomes in Trichomonas vaginalis (106). (B) Induction of cerebral malaria-like histopathology (37). (C) Discovery of new biomarkers for diagnostics in helminths (112). (D) Cell-free vaccines in malaria (30).